This invention relates generally to a system and method for managing or controlling energy utilization at a plurality of spaced sites and it also relates generally to an energy utilization controller. More specifically, the present invention relates to providing for the remote control of one or more energy management systems which operate heating, ventilating and air conditioning equipment at commercial or residential buildings.
Energy management is critical for environmentally conscious, cost-effective operation of buildings where heating, ventilating and air conditioning (HVAC) are used. Whereas in the past some types of energy management controls have been relatively static (e.g., a residential thermostat set at one desired temperature to be maintained throughout the day in a home), now there are dynamic energy management systems that can control HVAC systems on a highly variable schedule. To enhance the operation of these dynamic systems, there is the need for a remote control capability.
By way of an example, an electric utility company that serves thousands of customers may want to communicate a control signal to a large group of its customers to change their respective energy management systems when the electric utility experiences a peak load condition. The utility could have individual dedicated control circuits connected with each of its customers' energy management systems, but this would be expensive and inflexible. The electric utility could also automatically telephone each energy management system if each system is connected to a respective telephone circuit. This would be time consuming to dial each number and retransmit the same control data for each number if a large number of customers had to be contacted.
Other ways of providing remote communications to energy management systems being proposed and used today are fiber optic and hardwired cable systems. An advantage of these systems is that not only can remote signals from the utility control centers be supplied to a commercial or residential user but also additional information can be supplied such as telephone communications, cable TV, data communications through the information highway, etc. Disadvantages of these methods include: 1) large capital costs for material and labor to install fiber optic and cable systems, communication/signal transmission equipment required and right of way acquisition, and 2) difficulties in the installation process (e.g., tunneling under roadways, conflicts with existing buried utility cable and pipes).
Still further, a radio signal can be transmitted to receivers as is done in the following manner where air conditioning compressors can be turned on or off. As done in the past, electric utilities have provided residential customers with a local radio frequency receiver and a drum type ratchet timer for duty cycling the customer's air conditioning compressor. When the timers that have been provided to customers are to be activated, the electric utility transmits the appropriate radio frequency. For example, such an activating signal may be sent at 2:00 pm and a deactivating signal may be sent at 8:00 pm. During such an activation period, compressors could cycle "on" for fifteen minutes (for example) if otherwise called for by their respective thermostats, then "off" for fifteen minutes (for example) regardless of what their local systems do. This is a simple means of limiting the utility's summer electrical demand. A disadvantage of this system is that it simply provides an "on" or "off" signal; it does not communicate variable control data or instructions. Thus, the activated drum timer cycles on and off the same regardless of ambient conditions; therefore, during days of high outside temperatures, residential home temperatures could rise to uncomfortable levels. For example, during a one hour period while the drum timer is active, the air conditioning compressor runs for at most a cumulative time of 30 minutes and is off for at least a cumulative time of 30 minutes under the foregoing example of fifteen minute duty cycling. With hot outside temperatures and possibly low insulation values in a home, however, it may have been necessary to run the air conditioning compressor for forty-five minutes during the one hour to maintain a comfortable indoor temperature (i.e., if the compressor had not been disabled, the home thermostat would have called for the compressor to run forty-five minutes). If control signals for one or more variable parameters could be used, however, possibly more efficient control could be realized so that both reduced energy load and more reasonable comfort could be obtained.
Although remote control techniques can be implemented as suggested above, there is the need for an improved remote control technique whereby a number of energy management systems at different locations can be substantially simultaneously controlled with various control signals as selected by the sender. It would be desirable to implement such control relatively inexpensively. There is also the need for such a system to communicate a respective acknowledgement or other information back to the remote sender.